Process for making a laminated sheet

ABSTRACT

A process is provided for making stiff, lightweight laminate materials. At least one sheet of textured lamina having raised pointed structures is forced against a softer plain lamina so as to embed the structures therein. The pointed structures raised from grooves carved into the surface of the sheet material by means of a set of teeth carried on a knife element. The pointed structures may pierce through the softer lamina such that the protruding tips may be bent over or clinched to prevent their easy withdrawal. Two such texturized lamina may be used to sandwich and pierce through the softer lamina and are co-clinched by the other. In this way a light and stiff laminate is created.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. divisional application of U.S. patentapplication Ser. No. 14/568,462, entitled “PROCESS FOR MAKING ALAMINATED SHEET” and filed Dec. 12, 2014, which is a U.S. continuationapplication under 35 U.S.C. §111(a) claiming priority under 35 U.S.C.§§120 and 365(c) to International Application No. PCT/CA2013/000501,filed May 23, 2013, which claims the priority benefit of Canadian PatentApplication No. 2,780,397, filed Jun. 18, 2012, the contents of whichare incorporated by reference herein in their entirety for all intendedpurposes.

FIELD OF THE INVENTION

The invention relates to laminated materials, and more particularlyrelates to processes for laminating by layering of lamina or plies toproduce an improved structural material.

BACKGROUND OF THE INVENTION

There is a growing need for lighter, stiffer, cheaper structuralmaterials, preferably with all three qualities, with which to makebetter products.

SUMMARY OF THE INVENTION

A laminate is made by combining at least one harder lamina (layer) withat least one softer lamina. In one embodiment, two outer harder laminaare used to sandwich a softer core or centre lamina. The harderlamina(s) are preferably made of a ductile material such as sheet steel.Each such harder lamina has at least one face surface textured such thata myriad of pointed, nail-like, piercing structures rise therefrom.Preferably the textured lamina is not perforated. The core or centrelamina is preferably of a softer, pierceable material such as sheetplastic. One or more of the textured lamina(s) are forced against atleast one pierceable lamina so that it is thereby pierced and preferablypenetrated through such that the pointed tips of the piercing structuresare co-clinched against each other and thereby locking the three laminatogether.

According to a first aspect of the invention, a process is provided formaking a laminate sheet. At least one face of a sheet of a firstrelatively hard material is provided with a surface texture having aplurality of raised and generally pointed structures. The textured faceof the first material is then brought into contact with a face of asecond softer material. The two faces are forced together such that atleast some of the pointed structures enter the second material to form alaminate sheet.

Various materials may be used. In one preferred embodiment, the firstmaterial has a Brinell hardness of more than about 80, and the secondmaterial has a Brinell hardness of less than about 30. Preferably, thefirst material is a metal (e.g. steel). Preferably, the second materialis a plastic, resin, polymer, foam, rubber, wood, or hybrid material.

In one embodiment, the second material is a curable material, in whichcase, the “forcing” step includes applying the second material in apartially cured state, and then allowing the second material to cure.

The first and second materials may be forced together by passing thelaminate sheet (or portions thereof) between rolls. Preferably, theforcing step causes at least the tips of the pointed structures topierce through the second material, such that the tips protrude at asecond face of the second material. The protruding tips may be deformedto direct them over or onto or into the second face of the secondmaterial (e.g. by rolling over the tips with a roller, or by pressingdownward on the tips via a second sheet of the first material). The tipsmay also (but need not) interact with each other (deforming each otherby contact, or interengaging together in some embodiments).

The process may involve heating either or both of the first material andthe second material prior to forcing the materials together. Thematerials may be at least partially assembled together in a heated stateand then cooled. The second material may be heated to a softened state,prior to partially assembling the second material to the first materialin the softened state, and the second material may be then allowed tocool and at least partially harden, prior to further forcing thematerials together to form the laminate sheet.

The structures may have a hooked shape. The structures may be pre-bentinto a hooked shape.

According to a second aspect of the invention, a continuous process formaking laminate sheets is provided. A supply of sheeting of a firstrelatively hard material with a surface texture having a plurality ofraised and generally pointed structures is provided from a continuousroll. The textured face of the first material is brought into contactwith a face of a second softer material. The two faces are then forcedtogether such that at least some of the pointed structures enter thesecond material to form a laminate sheet.

The second material is preferably continuously fed to the firstmaterial, and the two materials are forced together downstream of therespective material feeds. Preferably, the second material iscontinuously rolled onto the first material. The first material may alsobe cut before the second material is applied (or pre-cut pieces may beprovided continuously for laminating—e.g. from a magazine).Alternatively, the laminate sheet may be cut into lengths after theforcing step.

A laminate sheet formed by any of the foregoing processes is alsoprovided.

According to a third aspect of the invention, a laminate sheet isprovided. A first relatively hard material with a surface texture havinga plurality of raised and generally pointed structures is mated to asecond softer material, such that at least some of the pointedstructures of the first material protrude into the second material.

At least some of the pointed structures may extend completely throughthe second material. At least some of the tips of the pointed structuresmay be turned over, onto or into the second material, so as to retainthe first and second materials together.

According to a fourth aspect of the invention, a multi-layer laminatesheet is provided. At least one dual sided sheet forms the core of thelaminate. The sheet is of a first relatively hard material and hassurface texturing on two faces thereof. The surface texture has aplurality of raised and generally pointed structures. Outer layers of asecond softer material are disposed on both sides of the dual sidedsheet, the second material being mated to the first material such thatat least some of the pointed structures of the first material protrudeinto the second material.

The multi-layer laminate sheet may also include boundary layers ofsingle sided sheets disposed respectively outside each of the outerlayers. Each boundary layer is single sided in that it has a pluralityof raised and generally pointed structures on one face thereof (theopposing face is plain). The structures on the face are disposed so asto extend into at least a portion of its corresponding outer layer. (Itwill be appreciated that laminates of greater complexity may also beprovided using this general structure—first boundary layer, core withone or more dual-sided textured sheets, each surrounded on both sideswith softer material, second boundary layer.)

In one variant, at least one outer layer has at least one recess forallowing access to the pointed structures. In another variant, one outerlayer has at least one relatively thinner area for allowing access tothe pointed structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a continuous process of producing a locked laminate sheetfrom three supply coils, the outer two lamina of having piercingstructures and the center lamina being of a softer pierceable material.The three lamina are forced and locked together between pressure rollswhich also causes the piercing structures to clinch against the opposingouter lamina. Heaters and/or coolers are shown that may be used to altermaterial hardness and thus its pierceability.

FIG. 2 shows an embodiment where two sets of pressure rollers are used(e.g. when the core lamina is too hard to be pierced at normaltemperatures, or too thick to be pierced through). The first rollersbegin the laminating, and the second roll set fully forces the laminatogether.

FIG. 3 shows detail of a textured lamina sheet with piercing structuresthat have a tapered cross-section ending in a pointed tip, populatingthe surface.

FIG. 3a shows detail of a variation using hooked structures (e.g. forembedment in a fluid core material such as cement or resin).

FIG. 3b shows how the piercing structures can be bent over to formbarbed hooks.

FIG. 4 shows the same embodiment where the structures have piercedthrough the adjacent lamina and where the pointed tips are above itssurface.

FIG. 5 shows two such piercing lamina having pierced through the softercore lamina and where the tips have been clinched in the process.

FIG. 6 shows an embodiment of a piercing lamina with both facestextured.

FIG. 7 shows another embodiment of five layer laminate where the twoouter lamina have single textured faces and the central textured laminahas both faces textured and where all three textured faces have piercedthe adjacent lamina and their pointed tips have been clinched.

FIG. 8 shows detail of the clinching where the tips are sequentiallyrolled down to the final clinched position on the face of the pierceablelamina.

FIG. 9 shows detail of a single piercing structure mostly embedded in aheat-softened core lamina, which may also be too thick to piercethrough.

FIG. 10 shows the same embodiment where the core lamina has been cooledback to hard and lamination completed by additional force causing aslight additional entry of the structure whereby a region of compressionis created about the piercing structure to retain it therein.

FIG. 11 shows another embodiment where the core material is the harderpiercing lamina textured on both faces and the outer lamina arepierceable and are forced onto the harder core.

FIG. 12 shows how a too-thick lamina may have the pointed structuresclinched by providing a recess into the lamina for a punch.

FIG. 13 shows exaggerated short portions of textured material. On right,the material is straight and the piercing structures are generallyparallel and at right angle to the surface. On left, is the same portionof material that has been curved to show how the piercing tips mustnecessarily become non-parallel or convergent, moving closer together.However, if the structures have pieced into a solid lamina (not shown),the tips are thereby locked in position and unable to move relative toeach other. This imparts a high degree of stiffness to the laminate.

FIG. 14 shows a fragment of a workpiece showing a single cutting planedfrom a trough in a surface of the workpiece.

DETAILED DESCRIPTION

In the following description the word “clinch” (clinching, clinchable,clinched), is used to describe the act of bending over the exposed tipof a pin- or nail that has pierced through two or more layers andextends therefrom. Clinching is common practice in the wood constructiontrade. Clinching is analogous to riveting in metal work, or to any otherdeformation of a fastener to prevent its easy withdrawal. The purpose ofclinching is to impart greater cohesion between the two laminate layersthat are so joined.

The term “pointed structure” or “pointed structures” is used herein as ageneral term to describe any type of nail- or pin-like structure (orhooked or barbed structure) raised on the surface of a material (forembedding or piercing). “Piercing structure” is one embodiment where thestructure is formed to pierce through a softer material in thelaminating process.

The term “pointed structure” or “pointed structures” is used herein as ageneral term to describe any type of nail- or pin-like structure (orhooked or barbed structure) raised on the surface of a material (forembedding or piercing). “Piercing structure” is one embodiment where thestructure is formed to pierce through a softer material in thelaminating process.

In the instant invention pointed (e.g. piercing) structures have beenraised from a surface of a harder lamina material. Preferably, they canpierce into an adjacent softer lamina and if longer than the softlamina's thickness, can protrude. The protruding tips may be bent overor clinched to create the ‘locked-laminate’ embodiment of the instantinvention. This piercing through and clinching brings the unexpectedbenefits of extraordinary stiffness to the resulting laminate.

FIG. 1 shows a process for making a continuous locked-laminate material.Coil 1 supplies the first lamina 1 a of softer pierceable material, suchas polyethylene, which will become the core lamina. Coils 2 and 2 asupply the outer second lamina 3 b and outer third lamina 3 c of hardermaterial each having one face 3 a textured with piercing structures 20.The three lamina layers are fed between pressure rolls 4, 4 a. Underpressure from rolls 4, 4 a, the piercing structures of the two outerlaminas 3 b, 3 c penetrate through the core lamina 1 a and are clinchedby the opposite outer lamina, continuously locking the three laminatogether which can then be severed into individual sheets 6 oflocked-laminate. Alternatively, the laminate 5 may be collected as abulk product on a take-up reel (not shown) (thus, the process may be acoil-to-coil process). The bulk product may be further cut or shaped forspecific applications, including cut-to-measure applications on a jobsite.

Rolls 4, 4 a can press against the entire width of the material“sandwich” or just in localized areas (e.g. edges).

If lamina 1 a is too hard to be readily pierced and/or too thick for thepiercing structures 20 to extend completely through it, heaters 10 maybe used to soften the material. Coolers 11 may then be used to cool thelaminate strip 5 prior to cutting into laminate sheets 6.

In another embodiment, stiff, sheet core lamina 1 b, such aspolycarbonate, shown in FIG. 2, may be similarly laminated between theouter textured lamina as described above, but with a variationcomprising using heaters 10 to enable partial piercing leaving a smallcontact gap of, say, 5% of structure height, between each lamina afterpassing through first rollers 4 c, 4 d. Coolers 11 then return thelamina 1 a to a harder state after which second rollers 4, 4 a completethe piercing and bring full contact. In this way the piercing structuresare forced a short distance into the too-stiff or too-thick core laminawhereupon a region of considerable compressive tension is created abouteach piercing structure and resulting in an unexpected retention force.Since these structures naturally have a tapered cross-section, asecondary taper-fit retention (well known in the mechanical field) isachieved adding further retentive strength. This all results in anexceptionally rigid, low-cost laminate suitable for a wide range ofuses. The sheets may be cut into shorter laminate pieces 6 a.

In FIG. 3 is shown the textured face 3 a and plain face 3 of harderouter lamina 3 b, 3 c which may be the same or of different materialssuch as steel-steel or steel-aluminum. Piercing structures 20 havepiercing, pointed tips 20 a. In FIG. 4 the tips 20 a are shown to piercethrough lamina 1 a and extend thereabove. FIG. 3a shows that thestructures can have a hook shape. For example, the hooks may beinherently formed in the initial process to prepare the textured outerlamina (for example, using the process described in co-pendingapplication “Bulk Textured Material Sheeting”, Canadian PatentApplication No. TBA, of the same applicants, filed in Canada on May 29,2012; or the process described for example in any of Canadian PatentNos. 1,330, 521; 1,337,622; or 2,127,339, the disclosures of all ofwhich are incorporated herein by reference). According to oneembodiment, the initial process used to prepare the textured outerlamina that inherently forms the hooks is a technique disclosed inCanadian Patent No. 2,127,339 that is applicable to readily machinablematerial, which is defined in the context of the embodiments of theinvention as a material from which a cutting blade may plane or gouge acontinuous cutting or shaving which can be smoothly curled out of thecutting plane without fracture. For example, by reference to theenlarged fragmentary view in FIG. 14, a tongue 16 (also referred toherein as a “pointed structure” according to one embodiment) is planedor gouged out of a surface 12 from a trough 14 which initially increasesin depth as a forming tool (e.g. forming tool 24 as shown in FIGS. 9 and10 of Canadian Patent No. 2,127,339) penetrates the surface 12 to adepth during translational movement and then continues at asubstantially constant depth as the translational movement of a cuttingedge of the forming tool continues, the resulting cutting beingdeflected in a curved path up a surface of the forming tool so as toform the tongue 16. Alternatively, more straight upright (e.g.nail-like) structures may be pre-bent into more hook-shape structures.Such pre-bending can be done using rollers or a press arrangementbetween flat platens so as to bend the thinner tips over into hooks. Thehook shape provides a means to engage or attach the textured surface 3 ato a flowable-type core material after which it solidifies encasing thehooks. For example such an arrangement can be used to secure thetextured face 3 a to an applied, non-cured or non-solid materials suchas cements, resins, melted polymers, adhesives and the like. In so doinga thicker core material 1 a can be used since the clinching does notrequire that the core be pierced through.

FIG. 3b shows how the structure tips 20 a can be further formed or bentover to form retroverted hooks or barbs 20 b. Such barbs can be used toadvantage to engage fabrics, soft lamina, and to be forced into heatedlamina. The barb shape is well known to resist removal which addsanother locking action to the instant lamination invention.

In FIG. 5 two harder outer lamina's structures are shown to have piercedright through core lamina 1 a such that their tips have been clinched bypressure against the opposing outer lamina creating the locked-laminateof the instant invention. FIG. 6 shows the harder lamina 3 with bothfaces textured with piercing structures such that it will be the corebetween two softer outer lamina (e.g. as shown in FIG. 7). In FIG. 7 thesame double textured lamina is shown as a core lamina with softerpierceable lamina on either side and with outer harder textured laminaon the outside creating a five layer lamination which can all beclinched together.

FIG. 8 shows only two lamina for clarity of the progression of the tips20 a being clinched while passing between rollers to the fully clinchedtip 20 b by being pressed together against a hard third surface such asan anvil. Also shown in FIG. 8 are examples of how the tips may bereverted 20 c so as to be pointing pack into the lamina, and crushed 20d where the effect is akin to riveting.

FIGS. 9 and 10 show a detail of one piercing structure 20 on lamina 3 aengaged almost fully into pre-softened lamina 1 c leaving a smallcontact gap 30 therebetween. After second pressing, post-hardened lamina1 d (lamina 1 c is cooled to normal hardness) is pierced an additionaldistance to close the contact gap and create a ‘compressive tensionenvelope’ 40 about the entire structure. This of course applies to allstructures in such a lamination process.

FIG. 11 shows the rolling lamination process applied to a core ofdouble-textured harder lamina 3 a with softer outer lamina 1 a whichouter lamina may be of the same or different materials and thickness.

In FIG. 12 is shown two different methods of clinching when too-thicklaminate prevents the tips from protruding. Flange 1 a′ provides athinner edge portion through which the piercing structures can emerge tobe clinched. Recess or cavity 41 into thicker lamina 1 e also providesthe same access to the tips for clinching. A clinching tool (e.g. smallroller or platen) may be pressed down into the recess 41 or at thethinner edge to locally clinch the exposed piercing structures. In thisway, specific areas of the laminate may be clinched and other areas not.

In FIG. 13 is shown a section of harder lamina 3 with exaggeratedpiercing structures having a generally parallel disposition at rightangles to the lamina face. When this same section is curved, thestructure tips must necessarily remain at right angles to the texturedlamina which they are intrinsic with, and protrude from, and so theirtips are shown to move together or converge at least somewhat. Ifhowever the illustrated section is part of the locked laminationmaterials detailed above, the tips are locked in position preventingtheir convergence which, in turn, imparts a high degree of resistance tobe bending where each structure adds resistance to bending. In this wayan exceptionally stiff laminate is created from relatively non-stifflamina. When the tips are clinched, a further substantial increase instrength is realized from the pull-apart or peel resistance that isthereby imparted to the lamination.

Such locked-laminate material may then be formed using different knownfabrication methods including bending, drawing, punching, and the like.Such fabrication methods may be augmented by heating the laminate toallow the structure's tips 50 a to move through the softened lamina totheir new angular relationship (FIG. 13), and then be locked there whenthe lamina cools back to normal hardness returning the desired stiffnessto the now-formed laminated sheet.

Although the foregoing description refers to three- and more-plylaminates, it will be appreciated that simple two-ply laminates can becreated using one harder (textured) material and one softer (pierceable)material, using the same roller arrangement described above (withsuitable modifications) to “lock” the material together.

The foregoing description illustrates only certain preferred embodimentsof the invention. The invention is not limited to the foregoingexamples. That is, persons skilled in the art will appreciate andunderstand that modifications and variations are, or will be, possibleto utilize and carry out the teachings of the invention describedherein. The scope of the claims should not be limited by the preferredembodiments set forth in the examples, but should be given the broadestpurposive construction consistent with the description as a whole.

1. A laminate sheet, comprising: a first sheet of metal and a secondsheet of metal, each sheet of metal having a respective face texturedwith a plurality of piercing structures, wherein each of at least someof the piercing structures has a respective clinched tip; a core laminasandwiched between the first sheet of metal and the second sheet ofmetal, the core lamina made from a material softer than the first sheetof metal and the second sheet of metal, wherein the piercing structuresof the first sheet of metal and the piercing structures of the secondsheet of metal pierce the core lamina, and the core lamina is locked tothe first sheet of metal and the second sheet of metal by the clinchedtips.
 2. The laminate sheet of claim 1, wherein at least a portion ofthe piercing structures extend completely through the core lamina suchthat the clinched tips thereof protrude from the core lamina.
 3. Thelaminate sheet of claim 1, wherein the first sheet of metal and secondsheet of metal are non-perforated.
 4. The laminate sheet of claim 1,wherein the at least one of the first sheet of metal and the secondsheet of metal is fabricated from steel or aluminum.
 5. The laminatesheet of claim 1, wherein the core lamina is made from plastic, resin,polymer, foam, rubber, wood, or a combination thereof.
 6. The laminatesheet of claim 1, wherein the clinched tips of the piercing structuresof the first sheet of metal are co-clinched with the clinched tips ofthe piercing structures of the second sheet of metal.
 7. The laminatesheet of claim 1, wherein the piercing structures have a hooked shape.8. The laminate sheet of claim 1, wherein the clinched tips are pointed.9. The laminate sheet of claim 1, wherein the laminate sheet is in acoil.
 10. A multi-layer laminate sheet, comprising: a sheet of metalhaving first and second opposed faces, each face textured with aplurality of piercing structures; and a first outer lamina on the firstface and a second outer lamina on the second face, the first outerlamina and the second outer lamina made from a material softer than thesheet of metal, wherein the piercing structures of the first face piercethe first outer lamina and the piercing structures of the second facepierce the second outer lamina.
 11. The multi-layer laminate sheet ofclaim 10, wherein each of at least some of the piercing structures has aclinched tip, and the sheet of metal is locked to the first outer laminaand the second outer lamina by the clinched tips.
 12. The multi-layerlaminate sheet of claim 11, wherein at least a portion of the piercingstructures extend completely through the first outer lamina, such thatthe clinched tips thereof protrude from the first outer lamina.
 13. Thelaminate sheet of claim 11, wherein the clinched tips are pointed. 14.The multi-layer laminate sheet of claim 10, wherein the sheet of metalis non-perforated.
 15. The multi-layer laminate sheet of claim 10,wherein the sheet of metal is fabricated from steel or aluminum.
 16. Themulti-layer laminate sheet of claim 10, wherein at least one of thefirst outer lamina and second outer lamina is made from plastic, resin,polymer, foam, rubber, wood, or a combination thereof.
 17. Themulti-layer laminate sheet of claim 10, wherein the piercing structureshave a hooked shape.
 18. The multi-layer laminate sheet of claim 10,wherein the laminate sheet is in a coil.
 19. The multi-layer laminatesheet of claim 10, wherein the first outer lamina comprises at least onerecess for allowing access to the piercing structures.
 20. Themulti-layer laminate sheet of claim 10, wherein at least one outer layerhas a thinned area for allowing access to the piercing structures.